What are your biggest struggles in learning JavaScript?

Tutorials and stackOverflow. For some reason Javascript tutorials often start with "In this tutorial we will write a simple ..." and, 12,000 lines later you can't remember what it was you were trying to learn.

And stackOverflow...OMG! Ask a simple question on SO like "Hey, these four lines of code are in an IIFE, where is variable foo visible?" and you'll get

• 9 comments asking why you are using an IIFE
• an argument regarding the use of the keyword var
• 14 reasons you should be using Python instead of Javascript
• a correction for a typo in one of your four lines
• a correction to the correction that insists the typo is intentional and within spec (with a link to a Fiddle to prove it)
• a complete refactoring of your four lines into ES8 to show how much simpler it will be
• the history of foo, bar, and baz

New JS programmers spend a lot of time in the magical incantation stage, copying and pasting random code from the web that they hope will run correctly but that they can't explain how it works. Some never escape it!

Back in the days, for me personally the most confusing thing was what 'this' actually is.
When I speak to many less experienced devs today, the most frequent struggle mentioned are 'scopes' and 'closures'.

Kind of silly, but sometimes knowing what some things are, but not knowing what they're called can be difficult or disheartening, especially in an interview or skill-building situation. Some examples that I've personally struggled with include, but are not limited to: closures, hoisting, various design patterns (module vs constructor vs API vs factory vs x100000 other ones), etc.

That feeling of inadequacy, followed by a realization that I actually knew what was being discussed all along (coupled with an "Oh, there's a name for that?") can take a while to shake off.

It can also be hard to discern "Is this a programming thing?" or "Is this a insert framework context here thing?" since JS is prone to having multitudes of vocabulary words being tossed around at any given time.

My entire dev career has been web, and I am really tempted to bash JavaScript here. :)

I will say that JavaScript has a lot of quirks which can bite you. Nowadays, a lot of libraries or preprocessors help by giving expressions of code which are more robust while staying on the happy path. But there continues to be a lot of churn in tooling and libraries around JavaScript to smooth out rough edges, especially given the (web) platform's popularity. So don't wear yourself out. I've put stuff into production on a lot of different platforms from pure JS to Angular that were "the new thing". Mostly to disappointment that the same problems were just in different places. Nowadays, I try to avoid writing JS code. For web UIs, I have been using Elm and my experience so far in maintaining its code has been very positive.

I was going to say this and scopes, but since it's mentioned already, I will say: Compilers and Presets and Browser Support!

There is so many to figure it out, TypeScript & Babel & ES2015 & ES2016 & ES2017 . and the whole ECMAScript 6 Compatibility with browsers, See This Compatibility Table for example.

Lots of good answers here, but I'd like to add that, due to JavaScript's history, people don't learn it the way they do other languages.

In my experience, when people pick up languages like Python or any of the C family, they grab a book and work through it. Along the way, they're learning how the language works and the ins and outs of how to solve problems using that language. So, things like syntax, common patterns, and the quirks of that language are naturally introduced.

With JavaScript though, new people just start grabbing at tutorials that show them HOW to do some specific thing or HOW to use some new framework. At no point are they learning actual JavaScript.

Learning React, Angular, Ember, Lodash, or any other plug and chug tool is not learning JavaScript. Going through a "What's new in ES6!" blog post is not learning JavaScript. Even learning Node is not learning JavaScript.

Read You Don't Know JS, all of it and actually LEARN JavaScript.

When first starting out as more of a hobbyist one of the first things I struggled with was how best to use objects and the object structure to store and use data. When to use OLOO vs. a class-like structure to properly scope functions, when to use prototypes, etc. Much of this has been "figured out" or at least made easier in the latest versions of ECMA which is nice.

Working with promises / async and chaining multiple things together to ensure state came together properly (in the jQuery days) and you didn't get "undefined" for your variable that logged just fine in the console was the next annoyance. Abstractions for these are pretty high quality now and somewhat easier to use but I definitely recommend gaining understanding before using otherwise it will bite you eventually :)

this (as has been said) is also an issue for me. Can still bite but at least I know to think "hey which this is this?" now.

Testing. Testing is super important but all the frameworks out there do it slightly differently and figuring out how to mock async / nested / imported stuff from scratch can be super hairy and difficult. I would still kill for an awesome tutorial on JavaScript testing practices. I wish I had started my testing discipline earlier so I had better muscle memory here.

DOM APIs are probably the hardest part. You never know all the nuances of each of those methods...

For instance, just yesterday I found a bug in my library because I used .offsetParent to get the first "positioned parent node", and I discovered that this property will give me the nearest "table" element if no positioned parents are available...

One: I can follow along with a tutorial no problem, understand what they're saying, write it all myself (instead of copy/paste) and all makes sense. Go to apply it on my own, either starting with a new project or adding it to something I was already working on - and I get a type of paralysis. Applying it on my own, without someone walking me through it, is regularly a huge hurdle for me. It's almost like my brain just isn't really absorbing it. Or so much of the other code (their styling and html and such) is taken care of that when I mix in the new stuff I don't know how it plays with everything else, because I didn't have to think of that in the walkthrough. I normally work it out and I'm fine, but it often stops me for awhile.

Two: Setting up my own dev environment. This still gets me almost every time, though I'm getting better. When you're learning the language so much is guided and focused on the actual language and on using tools that handle most of the other stuff for you. Which is great, in it's way....it's just hard when you go out on your own to really find a flow that works and lets you see what you're changing as you go.

1. As a complete beginner ,t he biggest trouble is finding the right guide(which or whose learning path should I follow ???).

2. Angular or React or Vue???(which front end framework)

3. ES5 , ES6, ES7 , ES8 ?????(How many things should I learn ???)

4. Babel , JSX and how many more ?